Gate driving circuit having a fault detecting circuit for a semiconductor switching device

ABSTRACT

Aspects of the invention are directed to a gate driving circuit for a power conversion circuit having an upper and lower arm circuit composed of series-connected upper arm and a lower arm, each arm including two or more semiconductor switching devices connected in series. In some aspects, a gate driving circuit of the invention includes a circuit of series connection including a diode and a resistor between a positive potential side of a positive side power supply and a positive electrode side. The gate driving circuit can determine a short-circuit fault of the semiconductor switching device that is connected to the gate driving circuit by detecting the current that flows through the circuit of series connection including the diode and the resistor when an OFF command of ON/OFF command signals is given to the semiconductor switching device.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on, and claims priority to, Japanese PatentApplication No. 2012-223842, filed on Oct. 9, 2012, the contents ofwhich are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the invention relate to gate driving circuits forseries-connected power semiconductor switching devices installed in highvoltage power conversion circuits.

2. Description of the Related Art

FIG. 7 shows an example of a two-level inverter circuit, which is apower conversion circuit for converting a DC power to an AC power. A DCpower supply 1 has a positive terminal P and a negative terminal N. Sucha DC power supply 1 can be generally composed from an AC power supplysystem by utilizing a rectifier and a high capacity capacitor, which arenot shown in the figure.

This power conversion circuit is a three-phase inverter circuit havingthe upper and lower arms for the U phase, the upper and lower arms forthe V phase, and the upper and lower arms for the W phase, the threepairs of upper and lower arms being connected in parallel between the Pterminal and the N terminal of the DC power supply 1. A load of an ACmotor 11 is connected to the U, V, and W terminals of the three-phaseinverter circuit. Since each phase has the same construction,description is solely given about the U phase. The power conversioncircuit of FIG. 7 uses IGTBs for semiconductor switching devices. Fourseries-connected IGBTs 2 through 5, each having ananti-parallel-connected diode, compose the upper arm, and fourseries-connected IGBTs 6 through 9, each having ananti-parallel-connected diode, compose the lower arm. Each arm comprisesa plurality of semiconductor switching devices connected in seriesbecause each switching device must be secured to withstand against ahigh voltage of the power supply 1 that is higher than the withstandvoltage of a single semiconductor switching device. The fourseries-connection in each arm is just an example, and an appropriatenumber of series connection is determined considering the voltage valueof the power supply 1 and the withstand voltage of the semiconductorswitching device.

A withstand voltage V_(CES) of a semiconductor switching device used inthe two-level inverter system can be determined by the rule of thumbbelow.Ed=V _(CES) ×n/2,where n is the number of series-connected devices in one arm and theV_(CES) is a withstand voltage between a collector and an emitter of thesemiconductor switching device.

Gate driving circuits 12 through 19 drive the respective IGBTs 2 through9 according to the signals given from a control circuit, which is notshown in the figure. Resistors 20 through 27 are connected between thecollector and emitter of the respective IGBTs 2 through 9 for thepurpose of equaling the voltage to which each of IGBTs, for exampleIGBTs 2 through 5, connected in series is subjected in the OFF state ofthe IGBTs.

FIG. 8 shows an example of gate driving circuit. A gate driving signal29 from a control circuit 28 is given to an upper arm gate drivingcircuit 30 and a lower arm gate driving circuit 31. An inverter gate 32is provided in order to deliver opposite signals to the upper arm andthe lower arm. Dead time circuits 33 and 34 that delay the rising uptime of an ON signal are provided in order to avoid overlapping of ONperiods of the upper arm IGBTGs 2 through 5 and the lower arm IGBTs 6through 9. Photo-couplers are provided in each gate driving circuit inorder to isolate a weak electric side (or a signal side) from a heavyelectric side (or a power side).

FIG. 9 shows the gate driving circuit more in detail. The gate drivingcircuit comprises: a photo-coupler 35 to isolate the input signal,transistors 36 and 37 to amplify a signal, a base resistor 38 for thetransistors 36 and 37, a gate resistor 39 to adjust the switching speedof the IGBT, and positive and negative power supplies 40 and 41 for thedriving circuit.

In short-circuit fault of an IGBT in another arm in general, if a normalIGBT is turned ON, power supply short-circuit occurs as shown in FIG.10. Whereas the explanation is made on a common two-level circuit, thesituation is in principle as same as in a multilevel circuit and acircuit having a plurality of IGBTs connected in series. In thissituation, the normal IGBT suffers from overcurrent and is subjected tothe power supply voltage between the collector and emitter of the IGBT.In order to detect this phenomenon, as shown in FIG. 9, a diode 42 isconnected to the collector of the IGBT S1. An ON command to the IGBT S1generates current flow into the diode 42 through a resistor 43. Sincethe collector-emitter voltage in an ON state of the IGBT is only severalvolts in a normal condition, the potential at the point B is alsoseveral volts. When a short-circuit current flows, the voltage betweenthe corrector and emitter of the IGBT S1 grows up to several hundredvolts; the diode 42 turns OFF, and the potential at the point B beginsto rise toward the voltage of the positive side power supply 40 of thegate driving circuit. However, the voltage is clamped by the voltage ofthe Zener diode 45. The Zener diode 45 turns ON and the transistor 46 inturn becomes an ON state. The potential of the gate of the IGBT S1equals the emitter potential of the IGBT, and thus, the IGBT S1 isforcedly turned OFF.

With the turning ON of the transistor 46, a current flows in thephoto-diode in the primary side of the photo-coupler 47 through theresistor 48. Thus, information of arm short-circuit is transmitted tothe photo-transistor in the secondary side of the photo-coupler 47. Theseries-connected circuit of the resistor 43 and a capacitor 44 is atimer circuit to prevent the transistor 46 from turning ON in theprocess of rising up of an ON signal and turning ON of the IGBT S1 untilthe collector-emitter voltage drops to several volts.

Japanese Unexamined Patent Application Publication No. 2008-118728 (alsoreferred to herein as “Patent Document 1”) discloses an example of aninverter circuit with each of upper and lower arms havingseries-connected IGBTs. Further, Japanese Unexamined Patent ApplicationPublication No. 2010-288416 (in FIG. 2 in particular) discloses anexample of gate driving circuit that detects a short-circuit fault ofthe other arm.

In a system having a plurality of series-connected IGBTs in each of theupper and lower arms as shown in FIG. 7, there are some discrepanciesbetween switching timings of the IGBTs, thus, each IGBT does not bearthe exactly equal voltage.

This inequality is usually taken into consideration in the design ofdielectric strength to determine a withstand voltage and the number ofseries connection of IGBTs. If the design value of voltage or current issurpassed in actual operation, however, the IGBT might break down.

When one device of series connected devices is short-circuited, theother normal devices must bear the voltage, which increases the voltagethat must be withstood by one device. The result is an avalanche ofbreakdown of the remained series-connected devices and breakdown of theentire arm finally occurs. When the entire arm, the upper arm in theexample shown in FIG. 11, is broken down and short-circuited, and theother arm, the lower arm in the example, is given an ON signal, DC powersupply short-circuit arises, which generates heavy short-circuit currentas indicated by the broken line, causing a large scale breakdown of theconverter circuit.

Patent Document 1 discloses a circuit for detecting a fault ofseries-connected semiconductor switching devices. This circuit however,needs a resistor for high power connected in parallel to the IGBT and inaddition, requires a circuit for detecting the current through theresistor or the voltage across the resistor. Thus, the circuit mayenlarge the device and raises the cost. Thus, as described above, thereexists certain shortcomings in the related art.

SUMMARY OF THE INVENTION

Embodiments of the invention address these and other shortcomings.Certain embodiments provide such a small-sized and low cost gate drivingcircuit having a circuit for detecting a fault of a semiconductorswitching device that detects a short circuit fault of a semiconductorswitching device without adding any component to the main circuit of thepower conversion circuit but only adding some electronic circuits intothe gate driving circuit.

A first aspect of the present invention is a gate driving circuit havinga circuit for detecting a short-circuit fault of a semiconductorswitching device, the gate driving circuit driving semiconductorswitching devices in a power conversion circuit for converting a DCpower to an AC power or converting an AC power to a DC power, the powerconversion circuit comprising a DC power supply and an upper and lowerarm circuit composed of an upper arm and a lower arm connected inseries, each arm comprising two or more semiconductor switching devicesconnected in series, each semiconductor switching device having ananti-parallel connected diode, and the gate driving circuit beingconnected in parallel to the DC power supply and the upper and lower armcircuit, wherein the gate driving circuit comprises a series circuitincluding a diode and a resistor between a positive potential terminalof a positive side power supply of the gate driving circuit and apositive electrode of the semiconductor switching device (the collectorelectrode of an IGBT or the drain electrode of a MOSFET), and determinesa short-circuit fault of the semiconductor switching device connectedwith the gate driving circuit by means of a current that flows throughthe series circuit including the diode and the resistor upon receivingan OFF command of ON/OFF command signals to the semiconductor switchingdevice.

A second aspect of the invention is the gate driving circuit having acircuit for detecting a short-circuit fault of a semiconductor switchingdevice according to the first aspect of the invention, wherein the gatedriving circuit comprises a circuit for detecting a power supplyshort-circuit current from the DC power supply that flows when the otherarm of opposing upper and lower arms becomes into a short-circuit faultstate.

A third aspect of the invention is the gate driving circuit having acircuit for detecting a short-circuit fault of a semiconductor switchingdevice according to the first or the second aspect of the invention,wherein the gate driving circuit comprises a bypass circuit thatprohibits current flow through the diode in the series circuit includingthe diode and the resistor upon receiving an ON command of ON/OFFcommand signals to the semiconductor switching device.

A fourth aspect of the invention is the gate driving circuit having acircuit for detecting a short-circuit fault of a semiconductor switchingdevice according to the first or the second aspect of the invention,wherein the series circuit including the diode and the resistor is aseries connected circuit comprising the diode, the resistor, andfurther, a Zener diode.

A fifth aspect of the invention is the gate driving circuit having acircuit for detecting a short-circuit fault of a semiconductor switchingdevice according to the first or the second aspect of the invention,wherein the series circuit including the diode and the resistorcomprises a primary side device of a photo-coupler disposed on a currentpath through the series circuit, and transmits a short-circuit faultstate of the semiconductor switching device to a secondary side of thephoto-coupler by means of a current flowing through the series circuitcomprising the diode, the resistor, and the photo-coupler.

A sixth aspect of the invention is the gate driving circuit having acircuit for detecting a short-circuit fault of a semiconductor switchingdevice according to the fifth aspect of the invention, wherein aphoto-coupler for detecting a short-circuit fault of a semiconductorswitching device in one of the upper and lower arms servessimultaneously as a photo-coupler for transmitting detection of an armshort-circuit current in a short-circuit fault of a semiconductorswitching device in the other arm to the secondary side of thephoto-coupler.

A seventh aspect of the invention is the gate driving circuit having acircuit for detecting a short-circuit fault of a semiconductor switchingdevice according to the sixth aspect of the invention, wherein the gatedriving circuit comprises a circuit, in the secondary side of thephoto-coupler, for determining whether a short-circuit fault hasoccurred in a semiconductor switching device in the own arm of the upperand lower arms or in a semiconductor switching device in the other armusing an ON or OFF switching command to the semiconductor switchingdevice.

An eighth aspect of the invention is the gate driving circuit having acircuit for detecting a short-circuit fault of a semiconductor switchingdevice according to any one of the fifth, sixth, and seventh aspects ofthe invention, wherein the signal transmission to a circuit disposed inthe secondary side of the photo-coupler is performed by means of anisolating component including an optical fiber and a transformer inplace of the photo-coupler.

The ninth aspect of the invention is the gate driving circuit having acircuit for detecting a short-circuit fault of a semiconductor switchingdevice according to the seventh aspect of the invention, wherein thegate driving circuit comprises a masking circuit that prohibitsdetermining operation during a dead time period in a process fordetermining, in the secondary side of the photo-coupler, whether ashort-circuit fault has occurred in a semiconductor switching device ofthe own arm or of the other arm using an OFF switching command to thesemiconductor switching device.

Embodiments of the invention include a gate driving circuit for a powerconversion circuit having an upper and lower arm circuit composed ofseries-connected upper arm and a lower arm, each arm comprising two ormore semiconductor switching devices connected in series. A gate drivingcircuit of embodiments of the invention comprises a circuit of seriesconnection including a diode and a resistor between a positive potentialside of a positive side power supply and a positive electrode side forexample collector electrode side of the semiconductor switching device.In some embodiments, the gate driving circuit determines a short-circuitfault of the semiconductor switching device that is connected to thegate driving circuit by detecting the current that flows through thecircuit of series connection including the diode and the resistor whenan OFF command of ON/OFF command signals is given to the semiconductorswitching device.

Consequently, a short-circuit fault of embodiments of the semiconductorswitching device is detected without additional component to the maincircuit of the power conversion circuit to interrupt the system safely.Therefore, the power conversion system can be achieved in a small sizeand at a low cost.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of gate driving circuit according to a firstembodiment of the present invention;

FIG. 2 shows a first operation mode in the example of gate drivingcircuit according to the first embodiment of the present invention;

FIG. 3 shows a second operation mode in the example of gate drivingcircuit according to the first embodiment of the present invention;

FIG. 4 shows a third operation mode in the example of gate drivingcircuit according to the first embodiment of the present invention;

FIG. 5 shows a fourth operation mode in the example of gate drivingcircuit according to the first embodiment of the present invention;

FIG. 6 shows an example of gate driving circuit according to the secondembodiment of the present invention;

FIG. 7 shows an example of two-level inverter circuit comprising amultiple of series-connected switching devices;

FIG. 8 shows an example of gate driving circuit according to atraditional technology;

FIG. 9 shows an example of conventional gate driving circuit that has anovercurrent protection circuit;

FIG. 10 is a schematic drawing to illustrate DC power supplyshort-circuit; and

FIG. 11 shows power supply short-circuit in a two-level inverter circuitcomprising a multiple of series-connected switching devices.

DETAILED DESCRIPTION

Embodiments of the invention provides, in the gate driving circuitthereof, a protection circuit technology that detects a short-circuitfault of one switching device and avoids expansion of the breakdown overa wide range of the conversion circuit. Here, the design of withstandvoltage of the switching devices, for example IGBTs, assumes that in thecase of a short-circuit fault of a single switching device, the IGBTsthat have not suffered breakdown can bear a specified withstand voltageowing to the situation in which an enough number of series connection ofIGBTs are provided, and a certain degree of margin is given to thewithstand voltage against a quasi-static turning OFF because thewithstand voltage has been determined in consideration of transientphenomena in the switching process and the unbalanced sharing ofvoltage.

A gate driving circuit of some embodiments is for a power conversioncircuit having an upper and lower arm circuit composed ofseries-connected upper arm and a lower arm, each arm comprising two ormore semiconductor switching devices connected in series. A gate drivingcircuit of some embodiments comprises a circuit of series connectionincluding a diode and a resistor between a positive potential side of apositive side power supply and a positive electrode side for example acollector electrode side of an IGBT or a drain electrode side of aMOSFET. The gate driving circuit determines a short-circuit fault of thesemiconductor switching device that is connected to the gate drivingcircuit by detecting the current that flows through the circuit ofseries connection including the diode and the resistor when an OFFcommand of ON/OFF command signals is given to the semiconductorswitching device.

[Embodiment Example 1]

FIG. 1 shows a gate driving circuit according to the first embodiment ofthe invention. In addition to the traditional circuit of FIG. 9 providedare a resistor 50, a Zener diode 51, and a diode 52 to detect ashort-circuit fault state of the IGBT on receiving an OFF command.Though omitted in FIG. 1, the transistors 36 and 37 for signalamplification shown in the traditional gate driving circuit of FIGS. 8and 9 can be provided in the circuit of the invention shown in FIG. 1.

To prohibit current flow through the Zener diode 51 and the diode 52under an ON command, a bypass circuit is provided that is a seriescircuit of a resistor 53 and a transistor 54 connected between theconnection point of the resistor 50 and a primary side diode of aphoto-coupler 47 and the emitter potential of the IGBT S1. A gatedriving circuit for the transistor 54 comprises resistors 67, 69, 70,72, a diode 68, and a capacitor 71 and turns fast the transistor 54 ONat rising up of an ON signal and turns with a certain delay thetransistor 54 OFF at falling down of the ON signal. Because it takes acertain period of time to actually turn OFF the IGBT even though an OFFcommand is given to a photo-coupler 35, the transistor 54 is maderemaining in an ON state during that period of time in order to preventsuch a current 66 as shown in FIG. 5 from flowing.

FIG. 2 shows an example of operation mode when an ON command is given ina normal state of the circuit of FIG. 1. The output of the photo-coupler35 turns to a high level (an H level) and a current 55 flows into thegate of the IGBT S1 to turn it ON. At the same time, a current 56 isdelivered to the base of the transistor 54 through the resistor 67 andthe diode 68 to turn the transistor 54 ON. Upon turning ON of thetransistor 54, a current 57 flows from a positive side power supply 40through the resistor 50 and the resistor 53. Here, the connection pointA between the resistor 50 and the resistor 53 is at a potential valuedetermined by dividing the voltage of the positive side power supply 40with the resistors 50 and 53. By setting this divided voltage to belower than the Zener voltage of the Zener diode 51, no current flowsthrough the primary side diode of the photo-coupler 47. Similarly to atraditional circuit, a current 59 flows upon turning ON of the IGBT S1through the resistor 43 and diodes 58 and 42.

FIG. 3 shows an example of operation mode when a short-circuit fault hasoccurred in an IGBT in the other arm of the opposing upper and lowerarms in the circuit of FIG. 1. The IGBT S1 is subjected to a highvoltage of several hundred volts as in a traditional circuit. Thecurrent 59 indicated in FIG. 2 does not flow but a current 60 flowsthrough a Zener diode 45 and the base of a transistor 46 to turn thetransistor 46 ON. As a result, the current that has been flowing throughthe gate of the IGBT S1 deviates from the IGBT S1 to become a current 61through a diode 49 and the transistor 46. The gate of the IGBT S1becomes at a potential equal to the emitter potential and the IGBT S1 isturned OFF forcedly. The turning ON of the transistor 46 allows currentflow 64 from the positive side power supply 40 through the resistor 50,the primary side diode of the photo-coupler 47, a diode 62, and aresistor 63. This current 64 transmits fault information to thesecondary side of the photo-coupler 47.

FIG. 4 shows an example of operation mode when an OFF command is givenin a normal state of the circuit of FIG. 1. The output of thephoto-coupler 35 becomes to a low level (an L level) and thegate-emitter of the IGBT S1 is reversely biased and a current 65 flowsto turn OFF the IGBT S1.

FIG. 5 shows an example of operation mode when an IGBT of the own arm inthe circuit of FIG. 1 is in a short-circuit fault state. Despite noinput of OFF command, the IGBT S1 undergoes virtually zero volts. Acurrent 66 flows from the positive side power supply 40 through theresistor 50, the primary side diode of the photo-coupler 47, the Zenerdiode 51, the diode 52, and the diode 42. Thus, a short-circuit faultinformation is transmitted to the secondary side of the photo-coupler47. The transmission of the fault information to the secondary side canbe carried out by means of an optical fiber or a pulse transformer, forexample, in place of the photo-coupler 47.

[Embodiment Example 2]

FIG. 6 shows the second embodiment of the present invention. The circuitof FIG. 6 determines whether a short-circuit fault has occurred in asemiconductor switching device of the own arm of the upper and lowerarms or in a semiconductor switching device of the other arm of theupper and lower arms, corresponding to a command signal of switching ONor switching OFF to the semiconductor switching device. FIG. 6 shows thecircuit in the primary side of the photo-coupler 35 and the circuit inthe secondary side of the photo-coupler 47. Logic circuits 73 and 74determine whether the other arm is in a short-circuited state or the ownarm is in a short-circuited state corresponding to the output of thephoto-coupler 47 and the command signal 72 from a dead time circuit 33to the IGBT S1. This circuit indicates a fault state by an ON state ofthe photo-transistor of the photo-coupler 47, that is, a low level ofthe output of the photo-coupler 47, and indicates an ON state of theIGBT S1 by a high level of the command signal 72 to the IGBT S1. Thelogic circuit 73 determines a short-circuit fault in the other armreceiving the signal 72 that is a signal 29 from a control circuit 28with a dead time added in a dead time adding circuit 33 and thesecondary side signal of the photo-coupler 47.

A short-circuit fault in the other arm is confirmed if a current flowsthrough the primary side diode of the photo-coupler 47 and the secondaryside photo-transistor turns ON when an OFF signal is given to the otherarm and an ON signal is given to the own arm. A short-circuit fault inthe own arm is identified by giving two signals to the logic circuit 74:one of the two signals is a signal 72 that is a signal 29 from thecontrol circuit 28 to which a dead time is added by the dead time addingcircuit 33, and the other signal is the secondary signal of thephoto-coupler 47 passed through a masking circuit 75 in a dead timeperiod. In other words, the short-circuit fault in the own arm isconfirmed if a current flows through the primary side diode of thephoto-coupler 47 and the secondary side photo-transistor turns ON whenan ON signal is given to the other arm and an OFF signal is given to theown arm. When a current is flowing through the diodeanti-parallel-connected to the IGBT S1 during the dead time period inwhich an OFF signal is given to the IGBTs of both of the upper and lowerarms, the collector-emitter voltage of the IGBT S1 is approximately zerovolts despite the OFF command input. Consequently, a short-circuit faultsignal is delivered from the photo-coupler 47 in the operation modeshown in FIG. 5. The masking circuit 75 in a dead time period put in thepreceding stage of the logic circuit 74 avoids erroneous determinationof a short-circuit fault in the own arm during a dead time period.

As explained above, the signal from the photo-coupler 47 in the own armenables discrimination between a short-circuit fault in the own arm anda short-circuit fault in the other arm. Therefore, it is possible in atwo level inverter circuit to eliminate the short-circuit faultdetecting circuit in the gate driving circuit of one of the upper andlower arms.

Whereas the embodiment example shown above is a gate driving circuit forone IGBT of a plurality of series-connected IGBTs, the gate drivingcircuits for the other series-connected IGBTs need to have the sameconstruction as the one described above. While the embodiment exampleshown above is related to an two-level inverter circuit, the presentinvention can be applied to multilevel conversion circuits of three ormore levels comprising a multiple of semiconductor switching devices andDC power supplies connected in series. The semiconductor switchingdevice can be a voltage-driven device such as a MOSFET as well as anIGBT. Although the power supply for the gate driving circuit is atwo-power supply system consisting of the positive side and negativeside power supplies 40 and 41 in the embodiment example described above,a single power supply system can be used as well.

Embodiments of the invention provide, in the gate driving circuitthereof, a control circuit technology for detecting a short-circuitfault of a switching device in a power conversion circuit having aplurality of semiconductor switching devices connected in series in onearm. Embodiments of the invention can be applied to high voltage motordriving equipment, power converters for system interconnection, andinstantaneous voltage drop compensator.

What is claimed is:
 1. A gate driving circuit having a circuit for detecting a short-circuit fault of a semiconductor switching device, the gate driving circuit driving semiconductor switching devices in a power conversion circuit for converting a DC power to an AC power or converting an AC power to a DC power, the power conversion circuit comprising a DC power supply and an upper and lower arm circuit composed of an upper arm and a lower arm connected in series, each arm comprising two or more semiconductor switching devices connected in series, each semiconductor switching device having an anti-parallel connected diode, and the power conversion circuit being connected in parallel to the DC power supply and the upper and lower arm circuit, the gate driving circuit comprising: a series circuit including a diode and a resistor between a positive potential terminal of a positive side power supply of the gate driving circuit and a positive electrode of the semiconductor switching device; wherein the gate driving circuit determines a short-circuit fault of the semiconductor switching device connected with the gate driving circuit by means of a current that flows through the series circuit including the diode and the resistor upon receiving an OFF command of ON/OFF command signals to the semiconductor switching device.
 2. The gate driving circuit having a circuit for detecting a short-circuit fault of a semiconductor switching device according to claim 1, wherein the gate driving circuit comprises a circuit for detecting a power supply short-circuit current from the DC power supply that flows when the other arm of opposing upper and lower arms becomes into a short-circuit fault state.
 3. The gate driving circuit having a circuit for detecting a short-circuit fault of a semiconductor switching device according to claim 1, wherein the gate driving circuit comprises a bypass circuit that prohibits current flow through the diode in the series circuit including the diode and the resistor upon receiving an ON command of ON/OFF command signals to the semiconductor switching device.
 4. The gate driving circuit having a circuit for detecting a short-circuit fault of a semiconductor switching device according to claim 1, wherein the series circuit including the diode and the resistor is a series connected circuit comprising the diode, the resistor, and a Zener diode.
 5. The gate driving circuit having a circuit for detecting a short-circuit fault of a semiconductor switching device according to claim 1, wherein the series circuit including the diode and the resistor comprises a primary side device of a photo-coupler disposed on a current path through the series circuit, and transmits a short-circuit fault state of the semiconductor switching device to a secondary side of the photo-coupler by means of a current flowing through the series circuit comprising the diode, the resistor, and the photo-coupler.
 6. The gate driving circuit having a circuit for detecting a short-circuit fault of a semiconductor switching device according to claim 5, wherein the signal transmission to a circuit disposed in the secondary side of the photo-coupler is performed by means of an isolating component selected from components including an optical fiber and a transformer in place of the photo-coupler.
 7. The gate driving circuit having a circuit for detecting a short-circuit fault of a semiconductor switching device according to claim 5, wherein a photo-coupler for detecting a short-circuit fault of a semiconductor switching device in one of the upper and lower arms serves simultaneously as a photo-coupler for transmitting detection of an arm short-circuit current in a short-circuit fault of a semiconductor switching device in the other arm to the secondary side of the photo-coupler.
 8. The gate driving circuit having a circuit for detecting a short-circuit fault of a semiconductor switching device according to claim 7, wherein the gate driving circuit comprises a circuit, in the secondary side of the photo-coupler, for determining whether a short-circuit fault has occurred in a semiconductor switching device in the own arm of the upper and lower arms or in a semiconductor switching device in the other arm of the upper and lower arms using an ON or OFF switching command to the semiconductor switching device.
 9. The gate driving circuit having a circuit for detecting a short-circuit fault of a semiconductor switching device according to claim 8, wherein the gate driving circuit comprises a masking circuit that prohibits determining operation during a dead time period in a process for determining, in the secondary side of the photo-coupler, whether a short-circuit fault has occurred in a semiconductor switching device of the own arm or of the other arm using an OFF switching command to the semiconductor switching device. 